Experimental investigation for vibration characteristics of jointed rocks using cyclic triaxial tests

Jointed rock specimens with planar, sawtooth and natural replicated joint types with a dip angle of 60 degrees were prepared, and a series of cyclic triaxial tests were performed at different confining pressures and cyclic deviatoric stress amplitudes subjected to 10,000 loading cycles to evaluate their effect on dynamic properties of the jointed rock specimen. Analysis of the test results indicated that the level of confining pressure and cyclic deviatoric stress amplitude along with the type of the joint had a significant influence on the dynamic characteristics of the jointed rock samples. With increasing confining pressure, the maximum residual axial strain attained decreased, while they increased with cyclic deviatoric stress amplitude for all the joint types. Jointed rock specimens subjected to cyclic loading responded with higher resilient moduli at higher confining pressures, while increasing cyclic deviatoric stress amplitude resulted in reduced resilient moduli. Furthermore, a higher confining pressure corresponded to a lower dissipated energy and damping ratio, while a higher cyclic deviatoric stress amplitude corresponded to a higher dissipated energy and damping ratio. With increasing number of cycles, the residual axial strains attained by the samples showed an increasing trend, especially during the initial phase of deformation. The resilient moduli illustrated a decreasing trend with number of cycles whereas dissipated energy and damping ratio showed a prompt decreasing trend within the first few cycles and then stabilised for all the joint types. Empirical relationships for the steady state resilient moduli and steady state damping ratio were developed through nonlinear regression analysis which incorporated the influence of confining pressure, applied cyclic deviatoric stress amplitude, shear strength and joint friction angle.

Automated summary

In this study, the dynamic properties of jointed rock specimens were investigated using cyclic triaxial tests. The results showed that the level of confining pressure, cyclic deviatoric stress amplitude, and joint type had a significant influence on the dynamic characteristics of the specimens. Increasing confining pressure and cyclic deviatoric stress amplitude led to higher residual axial strains and damping ratios, while reducing resilient moduli and dissipated energy. Moreover, the relationship between the number of cycles and the residual axial strain, resilient moduli, damping ratio, and dissipated energy was examined.